CONTINUOUSWAVE

What is the exact thickness of the hull [laminate] for a 1978 MONTAUK 17 where the bench seat fasteners are located?

I just reinstalled a loose bench seat with stainless steel lag screws in the spot where the hull cuts up to a thinner area

--Dave

The thickness of the fiberglass is a quarter-inch or less.

There is most likely no wood reinforcement in that location.

If there is not enough grip on the screw, slightly overdrill the hole. Loosen up the foam 1" deep and 1/4" to the side of the hole and then fill with epoxy (Locktite Marine Epoxy is easy to use). Let cure. Tap for the lag screw.

Another option is to NOT use a lag but rather a toggle bolt.

https://www.wholesalemarine.com/garelick-toggle-bolt-anchors-pair.html

The term "lag screw" usually refers to rather coarse-threaded large-diameter (a quarter inch and greater) fastener with a large hex head. Generally these would never be used on a Boston Whaler boat for holding in place a seat base.

Please explain in more detail that sort of fastener you used.

Usually on a Boston Whaler boat most hardware is attached with a stainless steel self-tapping screw, usually no larger than a No. 10, and there is already embedded wood in the hull to receive the fastener.

You cannot fasten anything large without having embedded wood in the hull at the location of the fasteners.

The location of embedded wood in the Unibond hull of a Boston Whaler boat will be shown on the wood locating diagram.

VIsit the REFERENCE section and read the article on the 16/17-foot hull. You will find links to the WOOD LOCATING DIAGRAMS applicable to your particular hull.

A list of drawings hosted here by the website is also available at

https://continuouswave.com/whaler/refer ... wings.html

Also, I am confused about the location of the "bench seat." A typical MONTAUK 17 will not have a bench seat.

Please explain what seat you are asking about that you earlier described as "a bench seat."